In article ,
"PhilC" writes:
In the interest of fuel saving could there be any saving in having a 12v
lighting circuit? Using maybe one or two larger transformers and the
equivalent of a mains lighting circuit or would the cost not be justifiable?

Possibly, but 12V is the wrong voltage. The most efficient 100W
filament lamp will be designed for 55V operation, so if you
were going to design a circuit for efficient filament lighting,
it would likely be at least 55V. I²R losses in the copper
will be very much higher than for mains lamps, and when you
factor in that and the consequential cost of thicker conductors,
you would probably go for a higher voltage.

In the US, a range of 85V filament lamps was produced. These
included a diode in the lamp base so they could be run from 120V
mains supply (RMS voltage of half-wave rectified 120VAC is 85V).
These were more efficient than the same power rated 120V filament
lamps, because they are nearer to the optimum filament lamp
operating voltage.

However, this is all rather academic now. No one who is concerned
with lighting energy efficiency will be using filament lamps any
more.

On a similar topic because transformers become warm, is there significant
electricity use when on standby?

Transformers aren't generally left on with no load. Actually,
electronic ones often won't work below a certain minimum load.

--
Andrew Gabriel